After World War II radial inflow turbines began to gain increasingly wide use in a wide range of applications due to their ease of manufacture, low cost, and high efficiency. Examples of these applications are gas turbines in aircraft auxiliary power units, turboexpanders for turbocharging in automotive vehicles, and turboexpanders in cryogenic air separation plants and gas liquefiers. In cryogenic plants, the turboexpanders usually operate continuously, and process large volumes of fluid. Energy input into a cryogenic plant is a principal cost, so that even small increases in efficiency in a cryogenic plant's turboexpanders are economically very beneficial.
The major losses in radial turbines are divisible into nozzle passage loss, rotor incidence loss, rotor passage loss, rotor discharge loss, and wheel disk friction loss. Radial turbine component losses can be measured by placing static pressure taps in the turbine gas path between the three major components: the inlet nozzle, the impeller and the exit diffuser. Analysis of field test data has shown that nozzle losses comprise a large part of the total turbine loss. Thus the aerodynamic configuration of the vanes comprising a radial inflow turbine nozzle present an opportunity for improvement.
Kirschner, Robertson, and Carter describe an approach to the definition of radial nozzle vanes in their July, 1971 NASA Lewis Research Center report CR-7288 entitled "The Design of an Advanced Turbine for Brayton Rotating Unit Application." In this work a vane camber line was generated from a prescribed distribution of loading on the vane. The thickness distribution of a 6-percent-thick NACA-63 airfoil was superimposed on the camber line. Surface velocities on this vane geometry were calculated, and minor adjustments in geometry were made until acceptable distributions were obtained.
Report No. 1390-5 dated Feb. 28, 1983, prepared by Northern Research and Engineering Corporation for the Department of Energy, designated DOE/ET/15426)T25 and entitled "R & D For Improved Efficiency Small Steam Turbines" describes another approach to the design of radial nozzle vanes. From process requirements, inlet flow conditions of temperature, pressure and flow angle to the radial nozzle, and downstream flow conditions of exit flow angle and velocity were selected. An aerodynamically ideal surface velocity distribution was selected, and the axial vane geometry to produce the selected velocity distribution was calculated by a computer program entitled BLADE. The axial vane coordinates were then mathematically transformed into radial coordinates.
This invention provides another method of designing and fabricating radial nozzle vanes and radial nozzles with novel features. This invention also provides a radial inflow turbine having a novel radial nozzle assembly and having improved efficiency over prior known radial inflow tubines.